SQL : date et heure automatiques lors de INSERT et UPDATE

Nouvelle table :

CREATE TABLE `users` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `email` varchar(100) NOT NULL,
  `firstname` varchar(30) NOT NULL,
  `lastname` varchar(50) NOT NULL,
  `password` char(32) NOT NULL,
  `created_at` datetime NOT NULL DEFAULT current_timestamp(),
  `updated_at` datetime DEFAULT NULL ON UPDATE current_timestamp(),
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

Table existante (avec les colonnes existantes) :

ALTER TABLE users
MODIFY COLUMN `created_at` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
MODIFY COLUMN `updated_at` datetime DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP;